Reliability-based seismic retrofitting design methodology for non-ductile reinforced concrete frame structures

This study presents a comprehensive, reliability-based methodology for the seismic retrofitting design of non-ductile reinforced concrete (RC) frame structures. Distinctively, it advances the innovative application of the Performance-Based Earthquake Engineering (PBEE) framework to the retrofitting of non-code-compliant buildings, an area where its use has been limited. By extending PBEE beyond its traditional scope, this research addresses critical challenges associated with assessing and improving the seismic performance of existing vulnerable structures. The proposed methodology offers a cost-effective strategy that balances seismic performance, quantified in terms of the Mean Return Period (MRP) of limit state exceedances, with retrofit costs. This performance-cost optimization enables the identification of retrofit solutions that achieve or surpass MRP targets while minimizing expenditure, thereby providing practical guidance for engineers and decision-makers. A central contribution of this work is the integration of collapse probability into the PBEE framework, enhancing the comprehensiveness of seismic risk assessment. This is particularly critical for existing non-ductile RC frame structures, which are inherently more vulnerable due to inadequate seismic detailing. The applicability and effectiveness of the proposed methodology are demonstrated through a case study involving the performance-based retrofit design of a representative structure. The results highlight the computational efficiency and accuracy of the proposed approach, validating its utility in real-world scenarios. This framework has the potential to inform and advance current practices in the seismic retrofitting of non-ductile RC frames, contributing to the enhanced safety, resilience, and sustainability of aging infrastructure in seismically active regions.